Nitration of aromatic hydrocarbons



March 26, 1940. J, MEISSNER 2,194,666

NITRATION OF AROMATIC HYDROCARBONS Original Filed Oct. 31, 1935 Josey?file/55H66 Patented Mar. 26, 1940 Original application October 31, 1935,Serial No.

47,727, mow Patent No. 2,135,012, dated November 1, 1938. Divided andthis application July QFFICE 16, 1937, Serial No. 154,086

Claims.

The invention relates to improvement in apparatus for the nitration ofaromatic hydrocarbons. The object of the invention is to provide anapparatus which allows continuous nitration 5 of hydrocarbons, and whichhas the advantage that a safe operation and a good output are obtainedwhile using an apparatus of very small dimensions. This application isfiled as a division of my copending application Serial Number 47,727,iiled October 31, 1935.

Heretofore, nitro-products of the kind referred to have been produced ina relatively large apparatus and by methods employing a number ofseparate operations. These methods were disadvantageous in that it wasvery diicult to dissipate the heat of reaction and to reduce the time ofreaction to a minimum. Other disadvantages, such as, incomplete mixingof the nitrating mixture and insuiiicient accessibility of the nitratingacid to the aromatic hydrocarbons to be nitrated are of special note.These disadvantages greatly iniuence nitration processes and reducetheir output considerably.

With the new apparatus it is possible to nitrate the aromatichydrocarbons thoroughly in one working step and to avoid thedisadvantages referred to above completely.

The new apparatus provides for continuous introduction of thehydrocarbons to be nitrated into the upper part of a vessel which isprovided with a pipe cooling system and continuous introduction of thenitrating acid into the lower part of said vessel whereby a forcedcirculation is obtained within the vessel, the nitrated material beingdischarged at the upper part of the nitrating vessel. By thisarrangement, a preliminary nitration is obtained in the upper part ofthe vessel as, at this point, the nitrating acid which has beenintroduced at the lower part of o the nitrating vessel has been partlyconsumed and therefore diluted, whereas the iinal nitration takes placein the lower part of the vessel where the fresh nitrating acid isintroduced.

In order to obtain a complete mixture of the nitrating components and toproduce an emulsion of the nitrating mixture by the introduction ofiinely divided air, the mixture within the nitrating vessel is stirredby an agitating device which has a mixing propeller at its lower partand 50 vanes for emulsifying purposes at its upper part.

A preferred embodiment of the invention is illustrated in theaccompanying drawing. This drawing shows a sectional view of theapparatus with which the new nitrating process is carried out.

Referring to the drawing, an upright nitrating vessel 8 is shownprovided with an upright pipe cooling system 6 which is in the form ofan annulus leaving free a central portion of the vessel and spacedbetween the top and bottom of the nitrating vessel, and an agitatingdevice 3 extending from the top of the nitrating vessel down through thecentral portion of the vessel left free by the pipe cooling system. Thisagita-ting device 3 comprises a shaft, the lower portion of which isprovided with a mixing propeller d for circulating the materials in thevessel down through the central portion of said vessel and up throughsaid pipe cooling system, and vanes 5 for emulsifying purposes. At thebottom of the vessel a valve 2 is provided for the introduction of thenitrating acid, whereas a pipe I is provided at the upper part of thevessel for the introduction of the hydrocarbons to be nitrated. Anopening i is provided in the upper portion of the vessel for dischargingthe products of the apparatus and an opening 9 is provided in the top ofvessel 8 toA permit access of air to the interior of the vessel.

After the apparatus has been filled with nitrating acid the material tobe nitrated, as for example, toluene, is introduced through the pipe I.At the same time the agitating device is started in order to obtain acomplete mixture of the component parts, which is very important forecent nitration. By the action of the agitating device, the mixture isnot only stirred but also emulsied as air is introduced into thenitrating mixture in a finely divided state. This causes a subdivisionof the nitrating mixture into small drops whereby a greater nitratingsurface is produced. This in turn causes an acceleration of thenitrating process and a more uniform product. It has been found that byemulsifying the mixture with air the formation of nitric oxides could beprevented almost entirely.

The air which is distributed inv the mixture in a very nely dividedstate makes possible a very quick separation of the nitrated materialAfrom the adhering waste acid in the separator (not shown). Byintroducing the nitrating acid into the lower part of the nitratingvessel at 2 the nitrating acid, which is diluted by the preliminarynitration, is replaced by the fresh acid and a iinal nitration isobtained at this point. This final nitration could previously only beobtained in several separated steps.

The fact that the nitrating mixture is forced through the space betweenthe cooling system 6 during the nitration process is of specialimportance. In this way the heat of reaction is dissipated more rapidlythan has been heretofore possible in the known nitrating devices.

The nitrating mixture discharged through the opening I at the upper partof the vessel is proportionate to the amount of aromatic hydrocarbonsintroduced into the upper part of the nitrating vessel and the amount ofnitrating acid introduced into the lower part of said vessel.

The advantages obtained with the new apparatus may be shortly summarizedas follows:

l. Continuous nitration which is obtained by the circulation of thenitrating mixture.

2. Great nitrating surface which is obtained by the intensive stirringof the nitrating mixture with an agitating device having a mixingpropeller and vanes for emulsiiying purposes, at spaced intervalsthereabove.

3. Prevention of the formation of nitric oxides which is obtained by theemulsitlcation of the nitrating mixture with air.

4. Accelerated separation of the nitrated mixture in the separator whichis caused by the presence of the air which is distributed in a nelydivided state in the mixture.

5. Intensive cooling of the nely divided nitrating mixture in thenitrating vessel which is obtained by the pipe cooling system.

6. Large output of a nitrating apparatus which has small dimensions,this feature being of special advantage when working with explosives.

While I have described herein some embodiments of my invention, I wishit to be understood that I do not intend to limit myself thereby exceptwithin the scope of the appended claims.

What I claim is:

l. An apparatus for the continuous nitration of aromatic hydrocarbonscomprising a nitratingvessel, a pipe cooling system comprising aplurality of vertical pipes adapted to be surrounded by a cooling mediumlocated within said vessel, a valve in the lower portion of said vesselfor introducing the nitrating acid, means in the upper portion of saidvessel for introducing the material to be nitrated, means in the upperportion of the vessel for discharging the nitrated mixture, mechanicalmeans disposed within said vessel for emulsifying the materialsintroduced into said vessel and mechanical means within said vessel forcirculating the said I. aterials through the pipes of said coolingsystem, said last two means being located in a space in the vesseladjacent to the pipe cooling system.

2. An apparatus for the continuous nitration of aromatic hydrocarbonscomprising a nitrating vessel, a pipe cooling system comprising aplurality of vertical pipes adapted to be surrounded by a cooling mediumwithin said vessel, a valve in the lower portion of said nitratingvessel for introducing the nitrating acid, means in the upper portion ofsaid vessel for introducing the material to be nitrated, means in theupper portion of said vessel for discharging the nitrated mixture, anagitating device in said vessel the lower portion of which comprises amixing propeller for circulating the materials 'introduced into thevessel through the pipes of said cooling system and the upper portion ofwhich comprises vanes for emulsifying the ma.- terials introduced insaid vessel said agitating device being located in a space in the vesseladjacent to the pipe cooling system.

3. An apparatus for the continuous nitratlon of aromatic hydrocarbonscomprising an upright vessel, an agitating device centrally disposed insaid vessel, said agitating device comprising a shaft, a mixingpropeller located on the lower portion of said shaft and emulsifyingvanes on said shaft at spaced intervals above said propeller, a verticalpipe cooling system within said vessel located between said agitatingdevices and the vertical walls of said vessel and spaced between the topand bottom walls o f said vessel, a valve in the lower portion of saidnitrating vessel for introducing the nitrating acid, means in the upperportion of said vessel for introducing the material to be nitrated, andmeans in the upper portion of said vessel for discharging the nitratedmixture.

4. An apparatus for the continuous nitration of aromatic hydrocarbonscomprising an upright vessel, an upright pipe cooling system within saidvessel, said system being in the shape of an annulus and leaving freethe central vertical portion of the vessel, means in the upper portionof the said vessel for introducing the material to be nitrated, valvemeans in the lower portion of the vessel for introducing the nitratingacid, an agitating device centrally disposed within said vesselextending from the top of said vessel to the lower portion of said pipecooling system, said agitating device comprising a shaft the 45 lowerportion of which is provided with a propeller adapted to circulate thematerials introduced into said vessel downwardly through the.

central vertical portion of the vessel and vanes at spaced intervalsabove said propeller for emulsifying the material introduced into saidvessel and means in the upper portion of the vessel for withdrawing thenitrated mixture from said vessel.

5. An apparatus for the continuous nitration of aromatic hydrocarbonscomprising an upright vessel, an upright pipe cooling system within saidvessel, said system being in the shape of an annulus and leaving freethe central vertical portion of the vessel, means in the upper portionof thc said vessel for introducing the material to be nitrated, valvemeans in the lower portion of the vessel for introducing the nitratingacid, an agitating device centrally disposed within said vesselextending from the top of said vessel to the lower portion of said pipecooling system, said agitating device comprising a shaft the lowerportion of which is provided with a propeller adapted to circulate thematerials introduced into said vessel downwardly through the centralvertical portion of the vessel and vanes at spaced intervals above saidpropeller for emulsifying the material introduced into said vessel andintroducing iinely divided air into such material and means in the upperportion of the vessel for withdrawing the nitrated mixture from saidvessel.

JOSEF MEISSNER.

